The present invention relates to devices for sampling and sequestration of polar organic chemicals from water so as to permit analysis thereof.
Global emissions of persistent bioconcentratable organic chemicals have resulted in a broad variety of adverse ecological effects and human suffering. Consequently, industry has developed less persistent, more water soluble chemicals. However, evidence is growing that the great quantities of these seemingly more environmentally friendly compounds (e.g., herbicides, new generation pesticides, and pharmaceutically related chemicals which have been historically viewed as totally benign) entering aquatic systems on a world-wide basis may be responsible for not only acutely toxic effects, but also are instrumental in causing sub-lethal chronic abnormalities. Adverse effects include altered behavior, neurotoxicity, and severely impaired reproduction. More insidious are the endocrine disrupting effects of exposure to the complex mixture of chemicals present in the environment. Numerous examples, such as increased vitellogenin levels (an estrogen controlled egg protein normally only found in females) in male fish from Las Vegas Wash near Lake Mead, Nev., nonfunctional testes in male alligators in Lake Apopka, Fla., reduced penis size in juvenile male otters in the Columbia River, feminized behavior in male western gulls in southern California, non-descended testicles in male Florida panthers, and masculinized female mosquito fish, unequivocally link such abnormalities to chemical exposures.
Although there are numerous reports on the negative effects of more polar endocrine disrupting chemicals on many forms of wildlife, a heated debate continues regarding the detrimental effects of these chemicals on human health. However, given the danger inherent in wildlife exposure to more water-soluble endocrine disrupting chemicals, and the potential deleterious effects resulting from prolonged human exposure, it is imperative that aquatic systems be monitored for the presence of a wide variety of polar organic chemicals currently entering the environment. While many techniques and methods are available to detect and quantify the non-polar organic contaminants, e.g., the DDT complex, polychlorinated biphenyls (PCBs), etc., of historic concern, similar approaches for waterborne polar organic contaminants are unavailable to environmental scientists. Monitoring of polar organic chemical species, potentially impacting wildlife and humans, and remediation of such contamination will be critical activities for the foreseeable future.
Although there has been considerable effort directed towards development of methods for actively sampling polar organic chemicals from water, this research has centered on the use of solid phase extraction employing specially modified polymeric resins in either a cartridge or imbedded in an inert membrane disk. See Hennion, M. C.; Pichon, V. 1994. Solid-Phase Extraction of Polar Organic Pollutants from Water. Environ. Sci. Technol., 28, 567A-583A; Barcelo/, D.; Hennion, M. C. 1997. Sampling of Polar Pesticides from Water Matrices. Anal. Chim. Acta, 338, 3-18; International Sorbent Technology. ISOLUTE Env+(copyright) The new generation of polystyrene polymer SPE columns. International Sorbent Technology, United Kingdom. Pihlstrxc3x6m, T. Hellstrxc3x6m, A.; Axelsson, V. 1997. Gas Chromatographic Analysis of Pesticides in Water with Off-line Solid Phase Extraction. Anal. Chim. Acta, 356,155-163. Hagen, D. F.; Markell, C. F.; Schmitt, G. A.; Blevins, D. D. 1990. Membrane Approach to Solid Phase Extractions. Anal. Chim. Acta, 236, 157-164. Hagen, D. F.; St. Mayr, S. J.; Errede, L. A.; Carr, P. W. 1989. Composite Chromatographic Article, U.S. Pat. No. 4,810,381, Mar. 7, 1989. Dumont, P. J.; Fritz, J. S. 1995. Effects of Resin Sulfonation on the Retention of Polar Organic Compounds in Solid Phase Extraction. J. Chromatogr. A, 691, 123-131; and Slobodnik, J.; Oztezkizam, xc3x96.; Lingeman, H.; Brinkman, U. A. th. 1996. The Solid Phase Extraction of Polar Pesticides from Environmental Water Samples on Graphitized Carbon and Empore-Activated Carbon Disk and On-line Coupling to Octadecyl-bonded Silica Analytical Columns. J. Chromatogr. A, 750, 227-238.
Laboratories conducting analytical and toxicological research concerning the presence and toxicity of polar organic chemical species critically need sampling and analytical methods capable of defining the presence and amounts of bioavailable polar organic chemical residues.
Unfortunately, current sampling methods are not integrative over sufficient time intervals to sequester adequate amounts of polar organic chemical residues (many of which may have toxicological significance even at ultra-trace levels) to detect trace to ultra-trace levels and to cost effectively detect episodic releases. Also, current sequestration methods are not adequate for integratively isolating sufficient amounts of the mixtures of potentially toxic polar organic chemicals present in aquatic systems for use with bioassay procedures for toxicity testing. It is apparent that no current sampling approach provides a truly integrative method for determining bioavailable polar organic chemical residues. Because no practical sampling method exists that enabled the determination of polar organic chemical species in a passive, integrative manner (existing methods are designed only for point in time monitoring and lack the sensitivity required) at trace to ultra-trace levels, there is a need for a passive, efficient, integrative, and high capacity sampler for polar organic chemical residues.
The present invention represents a new approach for dealing with major problems associated with toxic polar organic chemicals in the environment, which are of concern to the world at large as well to U.S. governmental agencies such as USGS, FWS, EPA, DOE, NIOSH, OSHA, DOD, etc. This invention can be calibrated for use as a monitoring tool for polar organic chemical residues dissolved in a wide variety of aquatic ecosystems. In addition, other embodiments of this invention can be provided which would apply to large-scale projects such as monitoring industrial emissions, and remediation of point source contamination and the associated release of toxic chemical residues into aquatic ecosystems.
Because the device of the invention can be configured for in situ passive integrative concentration of readily biologically available dissolved phase polar organic chemicals, the invention offers a widely applicable abiotic assessment of organism exposure, thereby overcoming a major shortcoming of current techniques used by government agencies.
Although the invention has other applications, the principal utility of the invention is in monitoring of the time-weighted average potential for exposure of humans and other living organisms to water borne polar organic chemical species. The invention is a very valuable tool for defining the source, transport, and fate/degradation of toxic polar organic chemical residues. Further, because of the integrative sampling construction of the device of the invention, the device is applicable to the reduction of polar organic chemical species in aquatic systems of limited areal extent. This invention is useful to resource managers, regulators, and scientists responsible for determining the impact of chemicals on fish and wildlife resources and human health. The device of the invention enables the measurement of the amounts of polar organic chemical residues present in a broad array of aquatic systems, prediction of their potential adverse effects, and in some cases potential remediation of unacceptably high levels of these chemicals. In brief, government agencies, private sector personnel and members of the scientific community involved in monitoring/regulating environmental contaminants, specifically polar organic chemical species, will have extensive application for this invention.
Before considering the device of the invention in more detail, reference will be made to some background considerations on which the invention is based. Polar organic chemicals enter the environment in a variety of forms ranging from ionic to neutral. Further, many organic chemicals undergo a wide array of biogeochemical-based transformations in the environment, and toxic polar organic chemicals generally impact organisms as dissolved, bioavailable species. Moreover, extensive experience with the dialysis of neutral molecules using nonporous polymeric films, the factors controlling sorption of chemicals by a broad array of solid media, and the reaction chemistry of organic chemicals has suggested that development of a passive integrative sampler for polar organic chemical species based on diffusion-controlled uptake of dissolved waterborne-polar organic chemical species and sequestration as non-mobile forms would be feasible.
In general, the device of the invention comprises a sealed microporous hydrophilic polymeric membrane enclosure containing a mixed sequestration phase capable of transforming the dissolved polar organic chemicals into non-mobile (sorbed) species, which accumulate in the device throughout the exposure time. The polymeric membrane is made of thin-walled microporous polymer such as polyethersulfone, nylon, hydrophilic polypropylene, acrylic copolymers, etc. In one embodiment, a thin layer of an appropriate polymer is grafted or laminated to a thicker microporous polymer, such as microporous polyethersulfone, to increase strength and to increase support of the sequestration media. Microporous membranes used in accordance with a preferred embodiment of the invention are characterized by air-filled fixed pores, with the air in the fixed pores being rapidly exchanged with water during the initial contact with water. In one preferred embodiment, the membrane is made of polyethersulfone, and the pores in the polyethersulfone membrane are 0.1 xcexcm in diameter. The polyethersulfone is hydrophobic as the bulk polymer, but becomes inherently hydrophilic as the polymerized membrane. Polyethersulfone is resistant to most organic solvents with the exception of chlorinated hydrocarbons and is stable in prolonged (xe2x89xa750 days) contact with water.
In accordance with a preferred embodiment, the sequestration phase comprises a triphasic admixture of a hyper-crosslinked polystyrene-divinylbenzene resin and a carbonaceous sorbent dispersed on a size exclusion styrene divinylbenzene copolymer. In advantageous implementation, the sorbent resin comprises Isolute ENV+(copyright), a third generation hyper-crosslinked polystyrene-divinylbenzene resin which has been optimized for the retention of very polar water-soluble organic chemicals. Modifications performed by the manufacturer of this sorbent have resulted in an inherent hydrophilicity, which allows wetting of the resin to occur without the use of organic solvents as intermediaries. Chemical sorption on the resin occurs by electron-donor interactions between the aromatic rings of the resin matrix and the aromatic or xcfx80 bonds of the analyte. The irregularly shaped resin particles have a surface area of 980 m2/g, an average particle size of 80 xcexcm, and an average pore size of 100 xc3x85. These attributes allow for high recoveries of a wide range of polar organic chemicals. This resin is also stable at any pH, unlike nearly all currently used solid phase sampling devices (i.e., silica-based resins).
The use of carbonaceous sorbents to concentrate organic chemicals has been employed in a wide variety of applications. However, recovery of the chemicals of interest from carbonaceous sorbents is often problematic due to the extreme affinity of activated carbons for organic chemicals. Another commercially available sorbent type, Ambersorbs(trademark), have proven effective in sequestering a variety of organic chemicals. Of these, the Ambersorb 1500 is the most hydrophilic and as with the Isolute ENV+(copyright), this sorbent readily wets without the use of organic solvents. However, as with nearly all carbonaceous sorbents, quantitative recovery of sequestered organic chemicals is problematic. To overcome the recovery problem associated with carbonaceous sorbents in accordance with a further aspect of the invention, a dispersion of Ambersorb 1500(trademark) on a polymeric size exclusion gel was prepared by an adaptation of the procedure described in U.S. Pat. No. 4,303,529, to Huckins, et al (see also Bouvier, E. S. P.; Iraneta, P. C.; Neue, U. D.; Mcdonald, P. D.; Phillips, D. J.; Capparella, M.; Cheng, Y. F. 1998. Polymeric Reversed-Phase SPE Sorbents-Characterization of a Hydrophilic-Lipophilic Balanced SPE Sorbent. Curr. Trends Sample prep. LC-GC, May, 1998, S53-S58.) In a specific preferred embodiment, the size exclusion gel comprises Bio Beads SX-3 (commercially available from BioRad, Inc, Hercules, Calif.). This polymeric gel is made from styrene-divinylbenzene copolymer with a 3% cross-linking of the polymer matrix. This degree of cross-linking results in the strongest adherence of carbon particles to the polymer gel. The binding of carbon particles to the polymer matrix is the result of electrostatic and covalent aromatic interactions between the two materials as well as partial inclusion of the carbon particles into the swelled gel pore structure during preparation of the carbon/polymeric gel sorbent. Optimal particle sizes for the carbon range from 0.1 to 50 xcexcm. Using the procedure previously described the average loading of Ambersorb onto the SX-3 gel was 5%. Other powdered carbons of the requisite size range may be similarly coated onto the SX-3 or similar polymer gels. The use of the limited amount of carbon as a sorbent expands the applicability of the sequestration media for concentrating polar organic chemicals from water, while simultaneously optimizing recovery of the polar organic chemicals from the sequestration media.
Other features and advantages of the invention will be set forth in, or will be apparent from, the detailed description of the preferred embodiments which follows.